Howdy, In 2.6, the PPC mm code for 4xx platforms uses large TLB entries for most of RAM. Specifically, I am looking at arch/ppc/mm/4xx_mmu.c at the mmu_mapin_ram function. In there, the pmd pointers are setup with _PMD_SIZE_16M | _PAGE_HWEXEC | _PAGE_HWWRITE.
Doesn't this allow the text pages of the kernel to be written to? So to my understanding, a buggy driver that went off into the weeds could corrupt the text pages of the kernel. I would think that you would want the kernel text pages to be non-writable so that if something like the above scenario happened you don't have possibly bad text pages. Debugging wouldn't be much fun. I think I am missing something here. If so, please excuse my lack of knowledge on TLBs, but I am somewhat new to the low level stuff. Anyone care to point out what I am missing? thx, josh ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
